Riding mowers having a zero radius turn (ZRT) capability are well known in the mowing art. Such mowers have a frame that carries a power source, such as an internal combustion engine, for propelling the frame over the ground and for providing power for mowing. Two powered rear drive wheels are carried on the frame with the front of the frame having a pair of unpowered front wheels, the wheels collectively supporting the frame for rolling over the ground. Often, the unpowered front wheels are caster wheels.
The rear drive wheels in a ZRT mower are individually powered by separate hydraulic drive motors that receive pressurized hydraulic fluid from a hydraulic system driven by the power source of the mower. The drive motors are individually controlled by separate control levers placed adjacent an operator's seat provided on the mower frame. The mower is steered by advancing one lever farther than the other to cause one drive motor, and thus the drive wheel on one side of the mower, to rotate faster than the other drive motor and drive wheel, thereby causing the vehicle to turn. Very sharp spin or ZRT type turns can be accomplished by advancing one control lever forwardly while pulling the other control lever rearwardly to cause the drive wheels on the opposite sides of the mower to simultaneously rotate in opposite directions.
A rotary cutting deck is carried at the front of the mower. The cutting deck usually houses a plurality of cutting blades that rotate about substantially vertical axes to cut grass in horizontal cutting planes. The blades are typically staggered relative to one another with a center blade being offset forwardly of a pair of side blades located on either side of the center blade. This allows the orbits of the cutting blades to overlap without having the blades contact one another, thus avoiding the need for timing the rotation of the blades. As the mower is driven over the ground and the blades are rotated, the blades cut a relatively large unbroken swath of grass during each pass of the mower. Exmark Mfg. Co., Inc. manufactures and sells ZRT mowers of this type under its Lazer Z brand name.
To change the height of cut (HOC) of the grass, the cutting deck is vertically moved up and down relative to the mower frame and thus relative to the ground to change the height of the cutting blades relative to the ground. In many known mowers, the HOC system used to do this includes multiple suspension links to the cutting deck. These movable links move up and down simultaneously with one another under the action of a single control lever. The control lever has a plurality of discrete adjusted positions relative to the mower frame, often established by the control lever engaging against a pin, to allow the height of cut of the cutting deck to be adjusted in a plurality of discrete increments. The height of cut is adjusted by changing the location of the pin within an array of adjustment holes provided therefor on the mower frame. The pin is selectively inserted by the operator into whichever adjustment hole corresponds to the desired height of cut.
The hydraulic system that powers the hydraulic motors that propel the drive wheels comprises one or more hydraulic pumps that are driven by the engine of the mower. In some cases, two separate pumps are used, one to power each hydraulic motor. Thus, four hydraulic components have to be mounted on the frame of the mower, namely two pumps and two motors. This presents various challenges in terms of finding or creating sufficient space on the frame of the motor to mount these components. Often, the frame of the mower is larger or taller than would be desirable due to the need to house the hydraulic components along with the other needed portions of the mower, such as the engine, battery, operator's seat, etc.
In addition, mower frames in mowers of this type often comprise relatively complicated weldments. These weldments typically have a number of side pieces that are welded together to extend from the front to the back of the mower along each side. These welded side pieces are then further welded to transverse cross members to form a unitary rigid frame. The side pieces that make up each side of the weldment along with the transverse cross members often restrict access to the interior of the frame. This complicates service, repair, maintenance or adjustment of the mower.